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Thread: some projection beam manipulation question

  1. #11

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    In pico DLP projectors two right angle prisms are used for directing the light beam onto the DMD chip and then towards the projector's imaging lens. X-cubes aren't used in smaller ones but are used in every 3LCD and 3DLP I know of. This is just anecdotal evidence from my observations and judging just by how it looks to the naked eye rather than a measurement with a sensor but it has appeared to me that with laser beams the light loss from prisms is more noticeable than with LEDs. There may be a reason behind it or it could just be me.

    Some chinese sellers sell "defective" trichroic cubes for much cheaper (around 10 USD) but I haven't gotten a clear answer from any of them why they are defective or what that means. They say they don't have scratches and produced by them rather than extracted from old equipment or taken from an old warehouse for old TVs/projectors. Maybe are the ones that haven't met a certain tolerance requirement or something along the lines. Considering the price I may just get two and check them out.

    There are also chinese sellers of "damaged" trichroic cubes with some scratches and also some scuffs around the edges of the prism. No idea where they get those and why they are as damaged as they are but they have quite a number in stock and sell them as "educational and decorative".

    You can find them on alibaba, aliexpress, banggood and gearbest and some damaged ones on ebay.

  2. #12
    Join Date
    Jan 2006
    Location
    Charleston, SC
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    2,147,488,263

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    Quote Originally Posted by shoujin View Post
    There are also chinese sellers of "damaged" trichroic cubes with some scratches and also some scuffs around the edges of the prism. No idea where they get those and why they are as damaged as they are but they have quite a number in stock and sell them as "educational and decorative".
    Sounds like pulls from used/decommissioned/RMA'd equipment.

    As a general (very general) rule, I've found that the smaller trichros from 3 CCD video cameras are higher quality than the larger cube trichros that come out of video projectors.

    Adam

  3. #13
    Join Date
    Mar 2015
    Location
    Cambridgeshire, England
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    368

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    I bought a set of the defective Chinese ones, they appear to be new but have chips on the edges. I have not tested them to see what the losses are yet, so they may be hopeless. I guess they are projector cubes as they also included some other optics that have a fresnel-like structure and stripes of dichroic material and look similar to the condenser optics from a projector I watched being stripped on YouTube.

  4. #14

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    Quote Originally Posted by NobleGas View Post
    I bought a set of the defective Chinese ones, they appear to be new but have chips on the edges
    I dont think chips on the edges should be an issue unless they managed to get in contact with the surfaces and scratch them.
    But it makes sense that they can't sell those as "new" and label it "defective". I wonder how they manage to get the edges of so many chipped during manufacturing because some of these sellers claim the defective ones are actually produce by them, unlike the sellers of damaged fresnels who admit they extract them.

    I have not tested them to see what the losses are yet, so they may be hopeless.
    If its from a projector it should work fine with LEDs but not sure if they can handle lasers. I know the cube is made up of prisms held together by an adhesive with similar refractive index. The laser may damage that.

    I guess they are projector cubes as they also included some other optics that have a fresnel-like structure and stripes of dichroic material and look similar to the condenser optics from a projector I watched being stripped on YouTube.
    Very likely. The fresnel-like lens is probably the flyeye lenses for making the beam homogenous and increase brightness uniformity across the DLP or LCD chip.
    I have not disassembled as many regular dized projectors so there may be other components used in those like regular fresnels or linear fresnels/lenticular.

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